Image forming apparatus of the type using electrophotography techniques is equipped with a beam light scanning device. The beam light scanner device has its light source, which is arranged by light-emitting elements such as laser diodes (LDs). In recent years, attempts are made to employ a plurality of LDs in order to speed up image formation operations. Output beams of individual LDs are guided to pass through a half mirror structure so that these are bundled together into substantially a single laser beam with prespecified beam intervals in a predetermined direction. The bundled laser beam is then guided to fall onto a polygon mirror.
An example of this scheme is disclosed, for example, in Japanese Laid-Open Patent Application No. 2001-91873 (FIGS. 1 and 7).
Unfortunately, the apparatus as taught thereby is faced with a problem which follows. Commercially available LDs for use as the light-emitting elements that emit beams of light are high in purchasing price in the marketplace. Thus, the use of an increased number of such LDs as the light emission means would result in an increase in production costs of a beam light scanner device and an image forming apparatus using such scanner.